Light emitting diode component

ABSTRACT

In a lighting package, a printed circuit board supports at least one light emitting die. A light transmissive cover is disposed over the at least one light emitting die. A phosphor is disposed on or inside of the light transmissive dome-shaped cover. The phosphor outputs converted light responsive to irradiation by the at least one light emitting die. An encapsulant substantially fills an interior volume defined by the light-transmissive cover and the printed circuit board.

This application is a continuation of application Ser. No. 11/312,268filed Dec. 20, 2005 now U.S. Pat. No. 7,800,121 which is acontinuation-in-part of application Ser. No. 10/831,862 filed Apr. 26,2004 and since issued as U.S. Pat. No. 7,224,000 which is acontinuation-in-part of International Application numberPCT/US2003/027363 with an international filing date of Aug. 29, 2003first published Mar. 11, 2004 as International Publication no. WO2004/021461 A2, which claims the benefit of U.S. Provisional ApplicationSer. No. 60/407,426 filed on Aug. 30, 2002. This application is also acontinuation-in-part of application Ser. No. 10/909,564 filed Nov. 2,2004 and since issued as U.S. Pat. No. 7,768,189.

This application incorporates by reference the content of applicationSer. No. 11/312,268, which has published as US 2006-0097245 A1. Thisapplication incorporates by reference the content of application Ser.No. 10/831,862, which has issued as U.S. Pat. No. 7,224,000 and haspublished as US 2005-0239227 A1. This application incorporates byreference the content of International Application numberPCT/US2003/027363. This application incorporates by reference thecontent of U.S. Provisional Application Ser. No. 60/407,426. Thisapplication incorporates by reference the content of application Ser.No. 10/909,564, which has published as US 2006-0022582 A1 and has issuedas U.S. Pat. No. 7,768,189.

BACKGROUND

The present invention relates to the lighting arts. It especiallyrelates to single-chip and multiple-chip light emitting diode componentsand methods for making same, and will be described with particularreference thereto. However, the invention applies to light emittingpackages generally, and is applicable in packaging monolithic lightemitting diode array dice, edge-emitting laser dice, vertical cavitylight emitting dice or monolithic laser array dice, organic lightemitting devices or organic light emitting array devices, and the like.The inventive light emitting packages and components will findapplication in substantially any application that employs one or morelight sources.

Light emitting diode components provide illumination in small, rugged,reliable packages. Light emitting diodes have been developed in manycolors spanning the visible spectrum and extending into the infrared andultraviolet. While each light emitting diode typically emits light in anarrow spectral range, primary color light emitting diodes can becombined to emit white light. In another approach for generating whitelight, light from a blue, violet, or ultraviolet light emitting diode iscoupled with a suitable phosphor to produce white light. Other colorscan similarly be generated by suitable selection of light emitting diecomponents, phosphors, and combinations of die components and phosphors.

One issue with light emitting diode components or packages relates tolight output intensity. Early light emitting diodes had low light outputintensities and were generally not competitive with incandescent andfluorescent light sources. Improvements in crystal growth, devicefabrication, packaging methods, phosphor materials, and the like havesubstantially improved the light output intensities of modern lightemitting diode packages. However, improvements in light outputintensities are still being sought.

Another issue with light emitting diode components and packages relatesto ruggedness. Commonly used packaging techniques, such as bonding ofthe dice to lead frames, can produce relatively fragile light emittingpackages. Moreover, light emitting diode components and packages tend tobe complex. A typical single-chip package may include, for example, alight emitting diode die, a lead frame, an encapsulant disposed over thelight emitting diode die and a portion of the lead frame, and a phosphorembedded in the encapsulant.

Multiple chip packages generally further increase complexity. Oneexample of such a multiple chip package is disclosed in Lowery, U.S.Pat. No. 6,504,301, which shows various arrangements involving generallywire-bonded interconnection of a plurality of light emitting dicedisposed on a support placed in a housing including a cylindrical casingand a fluorescent plate. A similar multiple chip package is disclosed inBaretz et al., U.S. Pat. No. 6,600,175. Baretz discloses a phosphorcontained in an encapsulant disposed inside the housing, The complexityof multiple chip packages such as those of Lowery and Baretz canadversely impact manufacturability, reliability, and manufacturingcosts.

Another issue with typical light emitting diode packages and componentsis operating lifetime. Performance of packages employing phosphorwavelength conversion of ultraviolet or short-wavelength visible lighttypically degrades over time due to discoloration or other degradationof the encapsulant or other materials caused by the ultraviolet orshort-wavelength visible light irradiation.

Another issue with typical light emitting diode packages is plug-incapability with lighting fixtures. A typical light emitting diodepackage is configured as a discrete electronic component and includes alead frame or other electronic component mounting arrangement designedfor solder connection. This approach is suitable for applications suchas visual power indicators. For illumination, however, the lightemitting diode package would desirably be used in a manner moreanalogous to a light bulb, fluorescent lighting tube, halogen bulb, orso forth, rather than as a discrete electronic component. To enableplug-in capability, the light emitting diode package for illuminationapplications should be readily connectable with existing illuminationfixtures such as Edison sockets, track lighting fixtures, or so forth.Such plug-in fixture compatibility is, however, hampered by thetypically high voltage and/or high frequency electrical power suppliedby such fixtures, which is not conducive to powering low-voltage lightemitting diode devices.

Another issue with using light emitting diode packages for illuminationis light output quality. When light emitting diode packages employseveral light emitting chips so as to produce high light intensity, aproblem arises in that the output consists of several approximate pointlight sources corresponding to the several chips. This pixelated spatialdistribution of light is problematic for illumination applications.

Spectral light output quality can also be an issue when using lightemitting diode packages for white illumination. For example, differentapplications may call for different color rendering index (CRI) values.Obtaining white light or substantially white light with a desired(usually high) CRI value in a commercially practical manner isdifficult. Existing cost-effective “white” phosphor compositionssometimes have relatively low CRI values.

The present invention contemplates improved apparatuses and methods thatovercome the above-mentioned limitations and others.

BRIEF SUMMARY

According to one aspect, a light emitting package is disclosed. Aprinted circuit board supports at least one light emitting die and hasat least two electrical terminals. Printed circuitry of the printedcircuit board connects the at least one light emitting die with the atleast two electrical terminals to provide power thereto. A lighttransmissive cover is disposed over the at least one light emitting diebut not over the at least two electrical terminals. The cover has anopen end defining a cover perimeter connected with the printed circuithoard. An inside surface of the cover together with the printed circuitboard defines an interior volume containing the at least one lightemitting die. An encapsulant is disposed in the interior volume andcovers at least the light emitting die.

According to another aspect, a light emitting package is disclosed. Asupport has at least one light emitting die disposed thereon. A glasscover is disposed on the support over the at least one light emittingdie. The glass cover and the support cooperatively define an interiorvolume containing the at least one light emitting die. An encapsulant isdisposed in the interior volume and encapsulates the at least one lightemitting die.

According to another aspect, a light emitting package is disclosed. Asupport has at least one light emitting die disposed thereon. A singlepiece light transmissive cover is disposed on the support over the atleast one light emitting die. The single piece cover and the supportcooperatively define a substantially closed interior volume containingthe at least one light emitting die. An encapsulant is disposed in theinterior volume and encapsulates the at least one light emitting die.

According to another aspect, a method is provided for making a lightemitting package. At least one light emitting die is electrically andmechanically connected to a printed circuit board. A light transmissivecover is secured to the printed circuit board. The light transmissivecover covers the at least one light emitting die. The secured lighttransmissive cover and the printed circuit board cooperatively define aninterior volume. An encapsulant is disposed in the interior volume.

According to another aspect, a method is provided for disposing of aphosphor on a surface. An adhesive is disposed on the surface. Aphosphor powder is applied to the adhesive. The adhesive is hardened.

According to another aspect, a lighting package is disclosed. A printedcircuit hoard supports at least one light emitting die. A lighttransmissive cover is disposed over the at least one light emitting die.At least one phosphor composition comprising at least one phosphorcompound is disposed on or inside of the light transmissive cover. Theat least one phosphor composition outputs converted light responsive toirradiation by the at least one light emitting die.

According to another aspect, a lighting package is disclosed. A printedcircuit board supports at least one light emitting die. A lighttransmissive cover is disposed over the at least one light emitting die.An encapsulant substantially fills an interior volume defined by thelight-transmissive cover and the printed circuit board.

According to another aspect, a lighting package is disclosed. A printedcircuit board supports at least one light emitting die. A lighttransmissive cover is disposed over the at least one light emitting die.Electrical power-conditioning circuitry is disposed on the printedcircuit board and is configured to condition received input power toenergize the supported at least one light emitting die.

Numerous advantages and benefits of the present invention will becomeapparent to those of ordinary skill in the art upon reading andunderstanding the present specification.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may take form in various components and arrangements ofcomponents, and in various process operations and arrangements ofprocess operations. The drawings are only for purposes of illustratingpreferred embodiments and are not to be construed as limiting theinvention.

FIG. 1 shows a perspective view of a lighting component or package.

FIG. 2 shows a perspective view of the printed circuit board of thelighting package of FIG. 1 with the light emitting dice or chips andassociated electrical components disposed thereon.

FIG. 3 shows a perspective view of the lighting component or package ofFIG. 1 with a portion of the light transmissive cover removed to showinternal elements of the lighting package.

FIG. 4 diagrams an example process for manufacturing the lightingpackage of FIG. 1,

FIG. 5 shows a perspective view of another lighting component or packagehaving backside electrical terminals.

FIG. 6 shows CRI tuning using a first phosphor composition havingphosphor compounds (A,B,C) and a second phosphor composition havingphosphor compounds (B,C,D).

FIG. 7 shows a high CRI spectrum achievable using the CRI tuning of FIG.6.

FIG. 8 shows a perspective view of another lighting component or packagehaving light emitting chips arranged in a long double-row. In FIG. 8, aportion of the light transmissive cover is removed to show some of thelight emitting dice or chips and other internal components.

FIG. 9 shows a perspective view of another lighting component orpackage, in which the light emitting dice and the phosphor areencapsulated by separate encapsulants. In FIG. 9, a portion of the lighttransmissive cover removed to show internal elements of the lightingpackage.

FIG. 10 diagrams an example process for manufacturing the lightingpackage of FIG. 9.

FIG. 11 shows a perspective view of another lighting component orpackage, in which the printed circuit board includes two evaporatedconductive traces. In FIG. 11, a portion of the light transmissive coverremoved to show internal elements of the lighting package.

FIG. 12 shows a perspective view of another lighting component orpackage having light emitting chips arranged in a double-row, with aplurality of dome-shaped light-transmissive covers disposed over thelight emitting chips.

FIG. 13 shows a side sectional view of another lighting component orpackage having a light transmissive dome-shaped cover on which twodifferent phosphor layers are disposed.

FIG. 14 is an enlarged sectional view of a portion of the lighttransmissive dome-shaped cover of FIG. 13, showing an optionalultraviolet reflective coating is disposed between the dome-shaped coverand the phosphor layers.

FIG. 15 shows a side sectional view of another lighting component orpackage having a light transmissive non-dome-shaped cover on which twodifferent phosphor layers are disposed.

FIG. 16 shows a perspective view of another lighting component orpackage similar to that of FIGS. 1-3, but having the phosphorcompositions screen-printed to display a corporate name and logo.

FIG. 17 is perspective view of a conventional LED package assembly.

FIG. 18 is a cross-sectional view of an LED assembly.

FIG. 19 is a cross-sectional view of an LED assembly.

FIG. 20 is a cross-sectional view of an LED assembly.

FIG. 21 is a cross-sectional vie of an LED assembly.

FIG. 22 is a side perspective view of an LED assembly.

FIG. 23 is a side perspective view of an LED assembly.

FIG. 24 is a representation of an LED assembly according to anembodiment depicting flux lines for radiation incident on its varioussurfaces.

FIG. 25 is a cross-sectional view of a lens for a blue LED sourcecontaining a band pass filter.

FIG. 26 is across-sectional view of a lens for a UV LED containingmultiple band pass filters.

FIG. 27 is a cross-sectional view of a lens containing an array of microor macro lenses is formed on the outer surface of the lens to controlthe emission angle, direction or intensity of the emitted radiation.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

With reference to FIGS. 1-3, a light emitting package 8 includes aprinted circuit board 10 on which one or more light emitting chips ordie are disposed. The printed circuit board is preferably substantiallythermally conductive. For example, a metal core printed circuit boardcan be employed. In the illustrated embodiment, three light emittingchips or dice 12, 14, 16 are disposed on the circuit board 10; however,the number of dice can be one die, two dice, or more than three dice.The die or dice can be group III-nitride blue or ultraviolet lightemitting diodes, red group III-phosphide or group III-arsenide lightemitting diodes, II-VI light emitting diodes, IV-VI light emittingdiodes, silicon or silicon-germanium light emitting diodes, or the like.As used herein, the term “ultraviolet” is intended to encompass lightemitting diode emission having a peak wavelength less than or about 425nm. In some contemplated embodiments, the die or dice are edge emittinglasers or vertical cavity surface emitting lasers. The light emittingchips or dice can also be organic light emitting diodes or devices. Eachlight emitting die or dice can be a bare die, or each die or dice caninclude an individual encapsulant. Still further, the die or dice can bea monolithic array of light emitting diode mesas, vertical cavitysurface emitting laser mesas, or the like. In the illustratedembodiment, the dice 12, 14, 16 are disposed in corresponding reflectivewells 22, 24, 26; however, the die or dice may be mounted on a planarsurface of the printed circuit hoard 10 or can be mounted on raisedpedestals or other elevated support structures. In some embodiments, aportion or all of the side of the printed circuit board 10 on which thelight emitting dice or chips 12, 14, 16 are disposed has a reflectivelayer disposed thereon to improve light extraction from the package 8.

With particular reference to FIG. 3, the illustrated printed circuitboard 10 includes one or more printed circuitry layers 30 sandwichedbetween insulative layers 32, 34. Typically, electrical pads are formedon the die attach surface of the printed circuit board 10 usingappropriate vias passing through the insulative layer 32 to electricallyconnect the dice 12, 14, 16 with the printed circuitry 30. The die ordice 12, 14, 16 can be mechanically and electrically attached to theprinted circuit board 10 in various ways, such as: by flip-chip bondingof die electrodes to electrical pads of the printed circuit board 10; bysoldering the die to the hoard 10 and using wire bonds to electricallyconnect the die electrodes with electrical pads of the printed circuithoard 10; by soldering the die to a lead frame (not shown) that is inturn mounted to the printed circuit board 10; or so forth. The dieattachment can include a sub-mount (not shown) disposed between a lightemitting die or chip and the printed circuit board or other support, orbetween the chip and a lead frame. In some embodiments, chip bonding isachieved using thermosonic bonding, thermocompressive bonding,ultrasonic bonding, eutectic bonding with or without underfill, or soforth. Still further, rather than mounting individual dice asillustrated herein, it is contemplated to employ a monolithic lightemitting diode array formed on a common substrate. In this contemplatedembodiment, the common substrate is soldered, thermosonically bonded,thermocompressively bonded, or otherwise secured to the printed circuitboard 10, and electrical connection to the individual light emittingmesas or structures is made by wire bonding, conductive traces formed onthe common substrate, or the like. Alternatively, a monolithic arrayhaving a transparent common substrate can be configured for a flip-chipmounting in which the electrodes of the light emitting mesas orstructures are directly bonded to electrical pads.

The printed circuit board 10 preferably further includes a heat sinkingstructure such as a ground plate or metal core 38 to provide heatsinking of the light emitting chips or dice 12, 14, 16. Optionally, aninsulative back-plate (not shown) is disposed on the side of the metalcore 38 distal from the die attach surface. The heat sink is optionallyomitted in lower power lighting packages, packages mounted on a heatsinking surface, or the like. Moreover, the printed circuitry layer orlayers 30 may provide adequate heat sinking in some embodiments. Instill yet other embodiments, the material or materials forming theinsulative layers 32, 34 are chosen to be thermally conductive so thatthese layers provide heat sinking.

The printed circuit board 10 optionally supports associated electricalcomponents, such as a zener diode component 44 including one or morezener diodes connected across the light emitting dice 12, 14, 16 by theprinted circuitry 30 to provide electrostatic discharge protection forthe dice. Similarly, electrical power conversion circuitry, powerregulating circuitry, voltage stabilizing circuitry, current-limitingcircuitry, rectifying circuitry, various combinations thereof, or thelike, can be included as additional components on the printed circuitboard 10. Such components can be provided as one or more discretecomponents, or as an application-specific integrated circuit (ASIC).Moreover, an electrical plug, adaptor, electrical terminals 46, or thelike can be disposed on the printed circuit hoard 10. In someembodiments, it is contemplated to include more than one set ofelectrical terminals, for example to enable series, parallel, orseries-parallel interconnection of a plurality of light emittingpackages. The printed circuitry 30 includes traces connecting theelectrical terminals 46 with the light emitting dice or chips 12, 14, 16such that suitable electrical power applied to the electrical terminals46 energizes the light emitting dice or chips 12, 14, 16 and associatedcircuitry (if any) such as the zener diode component 44, voltagestabilizing circuitry, current limiting circuitry, or so forth. Theprinted circuit board 10 can include other features such as a mountingsocket, mounting openings 50, 52 or the like for mechanically installingor securing the light emitting package 8.

The described printed circuit board 10 is an example. Other types ofprinted circuit boards or other support structures can also be employed.For example, the printed circuit traces can be disposed on the dieattach surface and/or on the bottom surface rather than being sandwichedbetween insulative layers 32, 34. Thus, for example, the printed circuithoard can be an electrically insulating support with a conductive traceevaporated and patterned or otherwise formed on the insulating support.Moreover, a heat sink can be substituted for the printed circuit board,for example with the light emitting die or dice soldered or otherwisemechanically secured to the heat sink and with the die electrodes wirebonded to electrical pads.

With continuing reference to FIGS. 1-3, the light emitting package 8further includes a light transmissive cover 60 disposed over the lightemitting dice or chips 12, 14, 16. The light transmissive cover has anopen end defining a cover perimeter 62 that connects with the printedcircuit hoard 10. In the illustrated embodiment, the printed circuitboard 10 includes an optional annular groove 66 that receives theperimeter 62 of the light transmissive cover 60, which in the lightemitting package 8 is a hemispherical dome-shaped cover. The groove 66guides in positioning the cover 60 on the printed circuit board 10, andoptionally also is used to help secure the cover to the board. In someembodiments the annular groove 66 is omitted, in which case theplacement of the cover 60 on the printed circuit board 10 is positionedby other means, such as by using an automated assembly jig.

The light transmissive cover 60 can be secured to the printed circuithoard 10 in various ways, such as by an adhesive, by a friction fitbetween the perimeter 62 and the groove 66, by fasteners, or so forth.The light transmissive cover 60 together with the printed circuit board10 define an interior volume 70 containing the light emitting dice orchips 12, 14, 16. In some embodiments, the connection between theperimeter 62 of the light transmissive cover 60 and the printed circuitboard 10 is a substantially airtight sealing connection thatsubstantially hermetically seals the interior volume 70. In otherembodiments, the connection between the perimeter 62 and the printedcircuit board 10 is not a hermetic seal, but rather may contain one ormore gaps, openings, or the like.

A phosphor 72 (indicated by a dotted line in FIG. 3) is optionallydisposed on an inside surface of the cover 60. If provided, the phosphoris selected to produce a desired wavelength conversion of a portion orsubstantially all of the light produced by the light emitting dice orchips 12, 14, 16. The term “phosphor” is to be understood as including asingle phosphor compound or a phosphor blend or composition of two ormore phosphor compounds chosen to produce a selected wavelengthconversion. For example, the phosphor 72 may be a phosphor compositionincluding red, green, and blue phosphor compounds that cooperativelyprovide white or substantially white light. In some embodiments, thetri-phosphor blend of (Ba,Sr,Ca)₅(PO₄)₃Cl:Eu²⁺, Sr₄Al₁₄O₂₅:Eu²⁺, and3.5MgO*0.5MgF₂*GeO₂:Mn⁴⁺ phosphors is used. In some embodiments, thephosphor compound (Ca,Sr,Ba)₂Si_(1−c)O_(4−2c):Eu²⁺ where 0≦c<0.25 isused alone or in combination with other phosphor compounds, and thephosphor is excited by a light emitting diode die or chip emittingradiation having a peak emission from about 200 nm to about 500 nm. Insome embodiments, the phosphor composition includes phosphor compounds(Ca,Sr,Ba)Al₂O₄:Eu²⁺, Sr₄Al₁₄O₂₅:Eu²⁺, and(Ca,Sr,Ba)MgAl₁₀O₁₇:Eu²⁺,Mn²⁺. For purposes of the present application,it should be understood that when a phosphor has two or more dopant ions(i.e. those ions following the colon in the above compositions), this ismeant to mean that the phosphor has at least one (but not necessarilyall) of those dopant ions within the material. That is, as understood bythose skilled in the art, this type of notation means that the phosphorcan include any or all of those specified ions as dopants in theformulation. In some embodiments, the phosphor blend is selected toprovide white light with color coordinates lying on or near theblackbody locus and a color temperature less than 4500K. In someembodiments, the phosphor blend is selected to provide white light withcolor coordinates lying on or near the blackbody locus and a colorrendering index (R_(a)) of 90 or greater.

Some various suitable phosphor compounds that can be used alone as asingle-compound phosphor composition and/or in combination with otherphosphor compounds as a multiple-compound phosphor composition arelisted here:

-   -   (Mg,Ca,Sr,Ba,Zn)₅(PO₄)₃Cl:Eu²⁺    -   (Ca,Sr,Ba)₂Si_(1−c)O_(4−2c):Eu²⁺ where 0≦c<0.25    -   (Ba,Sr,Ca)₅(PO₄)₃(Cl,F,Br,OH):Sb³⁺,Mn²⁺    -   (Mg,Ca,Sr,Ba,Zn)₅(PO₄)₃(F,Cl,Br,OH):Eu²⁺,Mn²⁺    -   (Ba,Sr,Ca)BPO₅:Eu²⁺,Mn²⁺    -   (Sr,Ca)₁₀(PO₄)₆*nB₂O₃:Eu²⁺    -   Sr₂Si₃O₈*2SrCl₂:Eu²⁺    -   Sr₄Al₁₄O₂₅:Eu²⁺    -   (Ca,Sr,Ba)MgAl₁₀O₁₇:Eu²⁺,Mn²⁺    -   Ba₃MgSi₂O₈:Eu²⁺    -   BaAl₈O₁₃:Eu²⁺    -   2SrO*0.84P₂O₅*0.16B₂O₃:Eu²⁺,    -   (Ba,Sr,Ca)Al₂O₄:Eu²⁺    -   (Y,Gd,Lu,Sc,La)BO₃:Ce³⁺,Tb³⁺    -   Ca₈Mg(SiO₄)₄Cl₂:Eu²⁺,Mn²⁺    -   (Ba,Sr,Ca)₂(Mg,Zn)Si₂O₇:Eu²⁺    -   (Sr,Ca,Ba)(Al,Ga,In)₂S₄:Eu²⁺    -   (Y,Gd,Tb,La,Sm,Pr,Lu)₃(Al,Ga)_(5−f)O_(12−3/2f):Ce³⁺ (wherein        0≦f≦0.5)    -   (Lu,Y,Sc)_(2−g)(Ca,Mg)_(1+g)Li_(h)Mg_(2−h)(Si,Ge)_(3−h)P_(h)O_(12−g):Ce³⁺        (wherein 0≦g≦0.5, 0≦h≦0.5)    -   (Ca,Sr)₈(Mg,Zn)(SiO₄)₄Cl₂:Eu²⁺,Mn²⁺    -   Na₂Gd₂B₂O₇:Ce³⁺,Tb³⁺    -   (Sr,Ca,Ba,Mg,Zn)₂P₂O₇:Eu²⁺,Mn²⁺    -   (Ca,Sr,Ba,Mg,Zn)₁₀(PO₄)₆(F,Cl,Br,OH)₂:Eu²⁺,Mn²⁺    -   (Gd,Y,Lu,La)₂O₃:Eu³⁺,Bi³⁺    -   (Gd,Y,Lu,La)₂O₂S:Eu³⁺,Bi³⁺    -   (Gd,Y,Lu,La)VO₄:Eu³⁺,Bi³⁺    -   SrY₂S₄:Eu²⁺    -   CaLa₂S₄:Ce³⁺    -   (Ca,Sr)S:Eu²⁺    -   (Ba,Sr,Ca)MgP₂O₇:Eu²⁺,Mn²⁺    -   (Y,Lu)₂WO₆:Eu³⁺,Mo⁶⁺    -   (Ba,Sr,Ca)_(u)Si_(v)(N,O)_(w):Eu²⁺    -   (Lu,Ca,Li,Mg,Y)alpha-SiAlON doped with Eu²⁺ and/or Ce³⁺    -   (Y,Lu,Gd)_(2−t)Ca_(t)Si₄N_(6+t)C_(1−t):Ce³⁺ (wherein 0≦t≦0.5)    -   3.5MgO*0.5MgF₂*GeO₂:Mn⁴⁺    -   A₂[MF₆]:Mn⁴⁺, where A=Li, Na, K, Rb or Cs and M=Ge, Si, Sn, Ti        or Zr    -   Ca_(1−d−e)Ce_(d)Eu_(e)Al_(1−d)(Mg,Zn)_(d)SiN₃.        Those skilled in the art can readily select other phosphor        compounds suitable for performing specific light conversions.

It should be noted that various phosphors are described herein in whichdifferent elements enclosed in parentheses and separated by commas, suchas in the above Ca_(1−d−e)Ce_(d)Eu_(e)Al_(1−d)(Mg,Zn)_(d)SiN₃ phosphor.As understood by those skilled in the art, this type of notation meansthat the phosphor can include any or all of those specified elements inthe formulation in any ratio from 0 to 100%. That is, this type ofnotation, for the above phosphor for example, has the same meaning asCa_(1−d−e)Ce_(d)Eu_(e)Al_(1−d)(Mg_(1−q)Zn_(q))_(d)SiN₃, wherein 0≦q≦1.

In some embodiments, a phosphor composition including phosphor compoundsSr₄Al₁₄O₂₅:Eu²⁺ and (Ca,Sr,Ba)MgAl₁₀O₁₇:Eu²⁺,Mn²⁺ are employed toproduce a green light suitable for use in application such as trafficsignals. Similarly, other listed phosphors are also suitable forproducing saturated colors and/or as phosphor compound components inwhite phosphor compositions.

In one embodiment, the light emitting dice or chips 12, 14, 16 are blue,violet, or ultraviolet emitters such as group III-nitride light emittingdiodes, and the phosphor 72 converts most or substantially all of thelight generated by the chips 12, 14, 16 into white light. In anotherembodiment the light emitting dice or chips 12, 14, 16 are blue lightemitters such as group III-nitride light emitting diodes, and thephosphor 72 is a yellow phosphor that converts some of the blue lightinto yellow light wherein direct blue light and indirect yellowphosphor-generated light combine to produce white light. In yet anotherembodiment the light emitting dice or chips 12, 14, 16 are blue, violet,or ultraviolet emitters and the phosphor 72 converts most orsubstantially all of the emitted light into light of a selected color,such as green, yellow, red, or so forth, so that the light emittingpackage 8 produces a colored light. These are examples only, andsubstantially any down-conversion of light produced by the lightemitting dice or chips 12, 14, 16 can be performed by suitable selectionof light emitting dice or chips 12, 14, 16 outputting at a selectedwavelength and suitable selection of the phosphor 72. In someembodiments, the phosphor 72 is omitted and the direct light produced bythe light emitting diodes 12, 14, 16 is the light output of the lightemitting package.

In some embodiments, the light transmissive cover 60 is a glass cover,where “glass” is not limited to silica-based materials but ratherencompasses substantially any inorganic, amorphous light transmissivematerial. Making the cover 60 of glass has certain advantages overplastic or other organic covers. Glass typically has better thermalstability than most plastics. Glass is more readily coated with opticalcoatings such as wavelength-selective reflective coatings,wavelength-selective absorbing coatings, or the like. Glass is alsotypically more resistant to scratching compared with most plastics.Moreover, glass has particular advantages in embodiments in which thelight emitting dice or chips 12, 14, 16 produce ultraviolet orshort-wavelength visible light, because light at these wavelengths candiscolor or otherwise degrade the optical quality of light transmissiveplastics over time. Optionally, a glass is selected which provides highreflectivity or absorption in the ultraviolet. In other embodiments, thelight transmissive cover 60 is made of plastic, Teflon, epoxy, EVA,acrylic, or another organic light transmissive material. In yet othercontemplated embodiments, the cover 60 is made of a crystalline lighttransmissive material such as crystalline quartz. Such crystallinecovers typically share many of the advantages of glass covers.

The printed circuit board 10 can include various reflective coatings orreflective surfaces for improving light extraction efficiency. In someembodiments, substantially the entire surface of the printed circuitboard on which the light emitting dice or chips 12, 14, 16 and the cover60 are disposed is reflective for both light produced by the lightemitting chips and for light produced by the phosphor 72. In otherembodiments, that portion or area of the printed circuit board surfacecovered by the cover 60 is reflective for both light produced by thelight emitting chips and for light produced by the phosphor 72, whilethat portion or area of the printed circuit board surface outside of thecover 60 is reflective principally for light produced by the phosphor72. These latter embodiments are suitable when substantially all of thedirect light produced by the light emitting dice or chips 12, 14, 16 isconverted by the phosphor, so that the output light is substantiallyentirely due to the phosphor. By using different reflective coatings orsurfaces inside of and outside of the cover 60, each reflective coatingor surface can be independently optimized for the spectrum of lightwhich it is intended to reflect.

It will be appreciated that the term “light transmissive” as used hereinto describe the cover 60 refers to the desired light output produced bythe light emitting package 8. The light output includes light generatedby the phosphor 72, if present, responsive to irradiation by the lightemitting dice or chips 12, 14, 16. In some embodiments, the light outputincludes a portion or all of the direct light produced by the lightemitting dice or chips 12, 14, 16. Examples of the latter embodimentsare a white light in which the white output light is a blending of bluelight emitted by the light emitting dice or chips 12, 14, 16 and yellowlight emitted by the phosphor 72, or embodiments in which the phosphor72 is omitted entirely. Where the direct light produced by the lightemitting dice or chips 12, 14, 16 contributes to the output light, thecover 60 should be at least partially light transmissive for that directlight. In embodiments where the output light is solely produced by thephosphor 72, on the other hand, the cover 60 may be light transmissivefor the phosphor output but partially or wholly reflective or absorbingfor the direct light produced by the light emitting dice or chips 12,14, 16.

An example of such a light emitting package is a white light emittingpackage in which the output white light is produced by the phosphor 72responsive to ultraviolet light produced by the light emitting dice orchips 12, 14, 16. The term “ultraviolet” is intended to encompass lightproduced by the light emitting dice or chips 12, 14, 16 whose peakwavelength is less than or about 425 nm. In such embodiments, includingboth an ultraviolet-reflective coating on the cover 60 and anultraviolet-reflective coating on the printed circuit board 10 caneffectively retain ultraviolet light produced by the ultraviolet lightemitting diodes within the interior volume 70 so that the ultravioletlight has multiple opportunities through multiple reflections tointeract with the phosphor 72, thus enhancing the ultraviolet-to-whitelight conversion efficiency. For retaining light, disposing theultraviolet reflective coating on the inside of the cover 60 isadvantageous to avoid ultraviolet absorption losses in the cover 60.Alternatively, the ultraviolet reflecting coating can be disposed on theoutside of the cover 60, or as an embedded layer or thin region withinthe cover 60.

The phosphor 72 can be applied to the inside surface of the lighttransmissive cover 60 using a suitable phosphor coating process, such asfor example, electrostatic coating, slurry coating, spray coating, or soforth. Moreover, the phosphor can be disposed elsewhere besides on theinside surface of the cover 60. For example, the phosphor can be appliedto the outside surface of the cover 60, using for example spray coating,outer surface coating, or the like, or to both the inside and outsidesurfaces of the cover 60. In yet another embodiment, the phosphor isembedded in the material of the light transmissive cover 60. However,phosphor is not readily embedded into most glass or crystallinematerials. In some embodiments the phosphor is disposed in a glassbinder that is spun onto or otherwise coated onto the inside and/oroutside surface of the cover 60.

In one suitable phosphor application process, the inside surface of thecover 60 is prepared by treatment with a liquid or low viscositysemi-solid material acting as a glue. The liquid material can be, forexample, liquid epoxy or silicone. The glue material can be applied in avariety of ways, such as by spraying, brushing, or dipping of itsworking formulation or a solution thereof in a suitable solvent such asacetone, methyl isobutyl ketone (MIBK), or t-butyl acetate. The phosphoris then deposited by dusting, dipping or pouring of phosphor in powderform, the choice of deposition method being based on the nature of theinside surface of the cover 60. For example, pour phosphor powder issuitably poured into the concave inside surface of the cover 60. On theother hand, dipping is generally a better method for coating the outsidesurface of the cover 60. The glue is then hardened by solventevaporation, thermal or UV curing, or the like to form the phosphorlayer.

Repetitions or various combinations of the above-described examplephosphor deposition and hardening processes may be performed, forexample to deposit more than one layer of phosphor or multiple layers ofphosphor blends, or as needed to attain a required thickness or layeredphosphor structure. Optionally, the phosphor coating may be covered witha final layer of clear glue or other suitable material to providemechanical protection, to filter out ambient ultraviolet light or excessradiation from the light emitting dice 12, 14, 16, or so forth.

As noted previously, the light transmissive cover 60 optionally includesone or more optical coatings besides the phosphor 72. In someembodiments, an anti-reflective coating is applied to the inside and/oroutside surface of the cover 60 to promote light transmission. Inembodiments in which the direct light produced by the light emittingdice or chips 12, 14, 16 does not form part of the output light, thelight transmissive cover 60 optionally includes a wavelength-selectivereflective coating to reflect the direct light back into the interiorvolume 70 where it has additional opportunity to interact with thephosphor 72.

In preferred embodiments, the light transmissive cover 60 is a singlepiece cover, such as a single piece glass cover, a single piece moldedplastic cover, or the like. Manufacturing the cover 60 as a single piecesimplifies assembly of the lighting package 8. Another advantage of asingle piece cover 60 is that a substantially hermetic sealing of theinterior volume 70 is obtained by ensuring a substantially hermetic sealbetween the perimeter 62 of the cover 60 and the printed circuit board10. The light transmissive cover 60 can include facets, fresnel lenscontours, or other light refractive features that promote lightscattering to produce a more spatially uniform light output. Similarly,the light transmissive cover 60 can be made of a frosted glass that hasbeen etched with sand or the like to produce light scattering.Optionally, the cover 60 includes an anti-shatter coating such asCovRguard™ (available from General Electric Company, GE LightingDivision, Nela Park, Cleveland, Ohio), Teflon, urethane, vinyl, or soforth.

With particular reference to FIG. 3, the interior volume 70 is, in thelighting package 8, substantially filled with an encapsulant 76. Theencapsulant 76 can be, for example, a silicone encapsulant, an epoxyencapsulant, or the like. The encapsulant 76 is at least partiallylight-transmissive or substantially transparent to light produced by thelight emitting dice or chips 12, 14, 16 and acts as a refractiveindex-matching material promoting light extraction out of the lightemitting dice or chips 12, 14, 16, and preferably also promoting lightcoupling with the phosphor 72 and, if the direct light produced by thelight emitting dice 12, 14, 16 directly contributes to the package lightoutput, also preferably promotes light transmission into the cover 60.

In some embodiments, the phosphor is dispersed in a binding materialthat is the same material as the encapsulant 76. In other embodimentsthe phosphor-binding material is a different material that has a goodrefractive index match with the encapsulant 76. In yet otherembodiments, the encapsulant 76 serves as the binding material for thephosphor 72. It will be appreciated that while the phosphor 72 is shownin FIG. 3 as residing substantially along the inside surface of thecover 60, in some embodiments the phosphor 72 may extend some distanceaway from the inside surface of the cover 60 and into the encapsulant 76disposed in the interior volume 70. In some contemplated embodiments,the phosphor is dispersed substantially into the encapsulant 76, and mayeven be uniformly distributed throughout the encapsulant 76. However, asdescribed in International Publication WO 2004/021461 A2, there areefficiency advantages to spatially separating the phosphor from thelight emitting dice or chips. Hence, in preferred embodiments thephosphor is disposed on the inside surface of the cover 60, or isdisposed closer to the cover 60 than to the light emitting dice or chips12, 14, 16. In some embodiments, light-scattering particles,particulates, or so forth are dispersed in the encapsulant 76 to providemore uniform light distribution.

In embodiments in which the light emitting dice or chips 12, 14, 16 arebare dice, that is, are not individually encapsulated, the encapsulant76 provides a common encapsulation of the light emitting dice or chips12, 14, 16 which protects the chips from damage due to exposure tomoisture or other detrimental environmental effects. The encapsulant 76may also provide potting of the light emitting dice or chips 12, 14, 16to improve the robustness of the lighting package 8 and make thelighting package 8 more resistant to damage from vibrations or othermechanical disturbances.

In some embodiments the cover 60 is sealed to the printed circuit board10, and the encapsulant 76 is injected into the interior volume 70 afterthe light transmissive cover is sealed. To enable encapsulant injection,openings 80, 82 are provided in the printed circuit hoard 10Alternatively, openings can be provided in the light transmissive coveror at the interface between the perimeter of the cover and the printedcircuit board. At least two such openings 80, 82 are preferablyprovided, so that while encapsulant material is injected into oneopening displaced air can exit via another opening. In otherembodiments, a single elongated or otherwise enlarged opening is used toprovide room for both the inflowing encapsulant and the outflowingdisplaced air.

In embodiments in which the interior volume 70 is substantiallyhermetically sealed, the injected encapsulant 76 can be a liquid ornon-rigid semi-solid encapsulant, such as an optical gel, that iscontained by the hermetically sealed interior volume 70. The liquid ornon-rigid semi-solid encapsulant may be left uncured in someembodiments, since the hermetic seal prevents leakage of theencapsulant. Moreover, a hermetic seal optionally allows the encapsulantto be injected under some pressure, so that the encapsulant is at apressure higher than atmospheric pressure. In some embodiments, theinterior volume 70 is not hermetically sealed, and some of the injectedencapsulant material may leak out. It will be appreciated that forencapsulant material of reasonably high viscosity, the amount of leakedencapsulant material is limited, and such leaked encapsulant materialmay even be advantageous insofar as it may help seal the interior volume70 when the injected encapsulant is cured or otherwise hardened into asolid.

With continuing reference to FIGS. 1-3 and with further reference toFIG. 4, an example process 100 for manufacturing the lighting package 8is described. The light emitting dice or chips 12, 14, 16 aremechanically and electrically connected with the printed circuit board10 in a die attach process 102. The die attach can involve flip chipbonding, soldering, wire bonding, or so forth. Separately, the insidesurface (and/or optionally the outside surface) of the lighttransmissive cover 60 is coated with the phosphor 72, if such phosphoris included in the package 8, in a phosphorizing process 104. As usedherein, the term “phosphorizing” denotes any method for putting aphosphor into the lighting package, such as coating or spraying aphosphor composition or compositions onto the light-transmissive cover,suspending phosphor particles in the encapsulant, embedding a phosphorin the light-transmissive cover, or so forth. In embodiments in whichthe cover has the phosphor embedded therein, the phosphorizing process104 is omitted and instead the phosphor is incorporated during moldingor other formation of the cover 60. The cover is then secured,optionally sealed, to the printed circuit board 10 in a sealing process106. The sealing process 106 defines the interior volume 70, which isoptionally a hermetically sealed volume. The encapsulant 76 is theninjected into the interior volume 70 through the openings 80, 82 in anencapsulant injection process 108. The encapsulant is cured in a curingprocess 110 if the encapsulant material requires curing. After injectionand optional curing of the encapsulant 76, the openings 80, 82 areoptionally sealed with a suitable sealing material in a sealing process112. In some embodiments, the encapsulant 76 also seals the openings 80,82, and so in these embodiments the separate sealing process 112 isomitted.

With reference to FIG. 5, another lighting package 8′ includes a printedcircuit board 10′ and a light transmissive cover 60′ having an open enddefining a cover perimeter 62′, which are illustrated in FIG. 5 andcorrespond to the printed circuit board 10, cover 60, and coverperimeter 62′, respectively, of the lighting package 8. The lightingpackage 8′ also includes most other components of the lighting package 8which however are not visible in the outside perspective view of FIG. 5.The lighting package 8′ differs from the lighting package 8 of FIGS. 1-3in that the electrical terminals 46 of the lighting package 8 arereplaced in the lighting package 8′ by four electrical terminals 46′disposed on the backside of the printed circuit board 10′. Theelectrical terminals 46′ are electrically connected with the lightemitting die or dice disposed in the cover 60′ by suitable printedcircuitry residing in or on the printed circuit board 10′. The backsideelectrical terminals 46′ can be configured, for example, to insert intomatching openings of a four-prong surface-mount receptacle socket.

With returning reference to FIGS. 1-3, in some embodiments the phosphorcomposition 72 includes a mixture of at least two constituent phosphorcompositions each possessing essentially the same emission colorcoordinates (for example x and y coordinates on the 1931 CIEchromaticity diagram) but different color rendering index (CRI) values.The at least two different constituent phosphor compositions aredifferent in that they differ by at least one phosphor compound. Forexample, the first constituent phosphor composition may include blue,green, and yellow phosphor compounds A, B, and C, respectively, with astoichiometry producing white or substantially white light at a firstCRI value; the second constituent phosphor composition may includegreen, yellow, and red phosphor compounds B, C, and D, respectively,with a stoichiometry producing white or substantially white light at asecond, different CRI value. In some embodiments, the blue, green,yellow, and red phosphor compounds A, B, C, and D are respectively(Ba,Sr,Ca)₅(PO₄)₃Cl:Eu²⁺, Sr₄Al₁₄O₂₅:Eu²⁺,(Ca,Sr,Ba)₂Si_(1−c)O_(4−2c):Eu²⁺ where 0≦c<0.25, and3.5MgO*0.5MgF₂*GeO₂:Mn⁴⁺. The output converted light consisting of ablending of the constituent converted light of the first and secondphosphor compositions has a CRI value that is different from, andpossibly larger than, the first or second CRI value of the individualconstituent phosphor compositions.

With reference to FIG. 6, which plots the 1931 CIE diagram with theblackbody locus BB superimposed thereon, the first phosphor composition(A,B,C) can have stoichiometries whose color coordinates span a trianglehaving as vertices the color points of the phosphor compounds A, B, andC. The second phosphor composition (B,C,D) can have stoichiometrieswhose color coordinates span a triangle having as vertices the colorpoints of the phosphor compounds B, C, and D. A cross-hatched trianglehaving as vertices the color points of the common phosphor compounds Band C and a third vertex E denote the range of color coordinates thatcan be achieved using suitable stoichiometries of either phosphorcomposition (A,B,C) or phosphor composition (B,C,D). In this range, CRItuning and/or luminosity tuning is achievable by blending or combiningthe first and second phosphor compositions with stoichiometriescorresponding to about the same color point. This approach enables CRItuning by selecting the ratio of the first (A,B,C) constituent phosphorcomposition and second (B,C,D) constituent phosphor composition. Moregenerally, at any given color point target, at least two constituentphosphor compositions are prepared, each constituent phosphorcomposition producing constituent converted light at substantially thesame color point responsive to irradiation by emission of the lightemitting die or chip 612 (preferably but not necessarily in theultraviolet range, such as peak chip emission wavelength less than orabout 425 nm). The number of phosphor compounds per constituent phosphorcomposition can be anywhere from one (such as, for example, suitablephosphor compounds disclosed in U.S. Pat. No. 6,522,065) to two, threeor more (such as, for example, suitable phosphor blends disclosed inU.S. Pat. No. 6,685,852). The disclosures of U.S. Pat. Nos. 6,522,065and 6,685,852 are incorporated by reference herein in their entirety. Tominimize color point variation, the at least two different constituentphosphor compositions should preferably provide substantially the samecolor point when excited by emission of the light emitting die or chip612, preferably to within about 0.020 units in both x and y colorcoordinates on the 1931 CIE chromaticity diagram, more preferably towithin 0.010 units, and still more preferably to within 0.005 units. Insome embodiments, the amount of the two constituent phosphorcompositions relative to each other is selected to optimize the lightoutput respective to color rendering index (CRI) at a given minimalluminosity threshold, or vice versa, at a selected color point.

By varying the ratio or blending of two or more constituent phosphorcompositions of substantially the same color point but different CRIvalues, one can alter the final CRI and luminosity characteristics ofthe device in a continuous fashion. By using a mixture of theconstituent phosphor compositions, a continuous range of CRI values areachievable. For some such mixtures, the CRI value of the blended lightmay be larger than the CRI value of any of the constituent phosphorcompositions acting alone. Advantageously, the CRI (e.g. maximize it fora given minimal luminosity requirement) or the luminosity (e.g. maximizeit for a given minimal CRI requirement) of the lighting device 608 istunable without affecting the chemical makeup of either the phosphorcompounds or the constituent phosphor compositions configured for thecolor point target. This affords a set of at least two constituentphosphor compositions to be used for the manufacturing of light sourceswith the same or similar color point but with CRI or luminosity valuescustomized for specific applications. Some suitable approaches foroptimizing or selecting the CRI using two or more constituent phosphorcompositions having about the same color coordinates are disclosed inco-pending application Ser. No. 10/909,564 filed Nov. 2, 2004 which isincorporated by reference herein in its entirety. In some embodiments,the at least two different constituent phosphor compositions areselected to provide white light with color coordinates lying on or nearthe blackbody locus and a color temperature less than 4500K.

With reference to FIG. 7, in some embodiments, the at least twodifferent constituent phosphor compositions are selected to blend toproduce white light with a color rendering index (R_(a)) of 90 orgreater. Example FIG. 7 shows a CRI-tuned converted light spectrum usinga mixture of the aforementioned (A,B,C) and (B,C,D) phosphorcompositions that provided a correlated color temperature of about 3300Kand a CRI value of about 90. When the blue or bluish bleed-throughdirect light emitting die radiation blending with the converted lightspectrum of FIG. 7 is also accounted for, the color temperature wasabout 3500K and the CRI value was about 91. Higher or lower CRI valuesare attainable at the same color point or another color point attainableby both phosphor compositions by varying the ratio of the phosphorcompositions, by using a technique such as Design of Experiment (DOE).

It is to be appreciated that the CRI-tuning mixture of phosphorcompositions (A,B,C) and (B,C,D) is an example. Other mixtures can beused so long as the constituent phosphor compositions produce convertedlight at about the same color point of interest. In some CRI tunedembodiments, the constituent phosphor compositions each produceconstituent converted light which is white light or substantially whitelight, that is, which lies on or substantially on the black body locusof the 1931 CIE chromaticity diagram. Such constituent phosphorcompositions are suitably operated in conjunction with one or moreultraviolet light emitting chips or dice, that is, with chips or dicethat emit peak radiation below or about at 425 nm. In these embodiments,the bleed-through light produced by the at least one light emitting diehas a negligible contribution to the visible spectrum of the convertedlight of the different phosphor compositions blended with bleed-throughlight produced by the at least one light emitting die. This negligiblecontribution can result from an arrangement in which the conversionefficiency of the light produced by the at least one light emitting dieis close to 100%. This negligible contribution can also result from theat least one light emitting die emitting light substantially outside ofthe visible spectrum.

In other CRI tuned embodiments, the output converted light produced byblending of the constituent converted light of the constituent phosphorcompositions combined with radiation produced by the at least one lightemitting die that bleeds through the phosphor layer 72 to contribute tolight output of the light emitting package 8 is white light orsubstantially white light, that is, lies on or substantially on theblack body locus of the 1931 CIE chromaticity diagram. In some suchembodiments, the phosphor compositions have color points correspondingto yellowish or orangish light and are suitably operated in conjunctionwith one or more blue light emitting chips or dice, that is, with chipsor dice that emit peak radiation in the blue or bluish visible range.The bleed-through blue or bluish light combines with the yellowish ororangish converted light to provide white light output of the lightemitting package. In other such embodiments, the phosphor compositionsproduce white or substantially white light with low intensity in theblue or bluish range, and the one or more light emitting chips or diceemit peak radiation in the blue or bluish visible range that bolstersthe spectrum of the blended light in the blue or bluish range of thevisible spectrum.

With reference to FIG. 8, another lighting package 8″ includes a printedcircuit board 10″, having a long strip shape, on which a plurality oflight emitting dice or chips 12″ are arranged in reflective wells 22″ ina double-row arrangement along the board strip. The printed circuitboard 10″ includes one or more printed circuitry layers 30″ sandwichedbetween insulative layers 32″, 34″, and a ground plate or metal core38″. Electrical terminals 46″ disposed on the printed circuit board 10″deliver electrical power the light emitting dice or chips 12″ via theprinted circuitry 30″. A light transmissive cover 60″ is tube-shaped tocover the long double-row of light emitting dice or chips 12″ and has anopen end defining a perimeter 62″ that is received by a matching groove66″ formed in the printed circuit board 10″. The tube-shaped cover 60″together secured to the printed circuit board 10″ define an elongated ortubular interior volume 70″ containing the light emitting dice or chips12″. A phosphor 72″ optionally coats an inside surface of thetube-shaped cover 60″. An encapsulant 76″ substantially fills theinterior volume 70″ to encapsulate and pot the light emitting dice orchips 12″ and the optional phosphor 72″. In some embodiments, it iscontemplated to replace the illustrated electric terminals 46″ withconventional fluorescent tube end-terminals, and to includepower-conditioning circuitry on the printed circuit board 10″ so thatthe lighting package 8″ is suitable for retrofit into a fluorescentlighting fixture.

With reference to FIG. 9, yet another lighting package 208 includes aprinted circuit board 210 on which one or more (specifically three inthe illustrated embodiment) light emitting dice or chips 212 arearranged. In the lighting package 208, the light emitting dice or chips212 are not disposed in reflective wells; rather, they aresurface-mounted to a level surface of the printed circuit board 210. Theprinted circuit board 210 includes one or more printed circuitry layers230 sandwiched between insulative layers 232, 234, and a ground plate ormetal core 238. A zener diode component 244 provides electrostaticdischarge protection for the light emitting dice or chips 212.Electrical terminals 246 disposed on the printed circuit board 210deliver electrical power to the light emitting dice or chips 212 via theprinted circuitry 230. A light transmissive cover 260 covers the lightemitting dice or chips 212 and has an open end defining a perimeter 262that is connected with the printed circuit board 210 to define aninterior volume 270 containing the light emitting dice or chips 212. Aphosphor 272 optionally coats an inside surface of the lighttransmissive cover 260. The above-described elements of the lightingcomponent or package 208 are similar to corresponding elements of thelighting component or package 8 shown in FIGS. 1-3.

The lighting package 208 differs from the lighting package 8 in theconfiguration of the encapsulant disposed in the interior volume. In thelighting package 208, a first encapsulant 276 encapsulates andoptionally pots the light emitting dice or chips 212, but does notsubstantially fill the interior volume 270. In some embodiments, thefirst encapsulant 276 may encapsulate only the one or more lightemitting dice 212. A second encapsulant 278 encapsulates the phosphor272 if such a phosphor is included in the package 208. In someembodiments, the second encapsulant 278 is the binding material of thephosphor 270. For example, the phosphor 272 may be applied to the insidesurface of the cover 260, and the encapsulant in this embodiment is thebinding material of the applied phosphor. Generally, the first andsecond encapsulants 276, 278 can be different materials. A substantialgap 280 extends between the first and second encapsulants 276, 278.Typically, the gap 280 contains air; however, it is also contemplated tofill the gap 280 with an inert gas to reduce moisture in the lightingpackage 208. In yet another embodiment, the gap 280 is filled with athird encapsulant different from at least one of the first and secondencapsulants 276, 278. In the lighting package 208, there is no groovein the printed circuit board 210 for receiving the perimeter 262 of thecover 260. However, such a groove similar to the groove 66 of thelighting package 8 can optionally be provided to align and optionallyhelp secure the cover 260 to the printed circuit board 210.

With continuing reference to FIG. 9 and with further reference to FIG.10, an example process 300 for manufacturing the lighting package 208 isdescribed. The light emitting dice or chips 212 are mechanically andelectrically connected with the printed circuit board 210 in a dieattach process 302. The die attach can involve flip chip bonding,soldering, wire bonding, or so forth. The attached light emitting dice212 are encapsulated or potted on the printed circuit board 210 in afirst encapsulation process 304, and the first encapsulant 276 is curedin a first curing process 306 applied to the printed circuit board 210.

Separately, the inside surface (and/or optionally the outside surface)of the light transmissive cover 260 is coated with the phosphor 272 in aphosphorizing process 310. In embodiments in which the cover has thephosphor embedded therein, the phosphorizing process 310 is omitted andinstead the phosphor is incorporated during molding or other formationof the cover 260. The phosphor is encapsulated on the light transmissivecover 260 in a second encapsulation process 312, and the secondencapsulant 278 is cured in a second curing process 314 applied to thelight transmissive cover 314. If the phosphor 272 is omitted from thepackage 208, then process 310, 312, and 314 are suitably omitted. Insome embodiments the second encapsulant 278 is the binding material ofthe phosphor 272; in these embodiments, the phosphorization process 310and the second encapsulation process 312 are integrated. The lighttransmissive cover is then secured, optionally sealed, to the printedcircuit board 210 in a securing process 316. The securing process 316defines the interior volume 270, which is optionally a hermeticallysealed volume.

With reference to FIG. 11, still yet another lighting package 408includes a printed circuit board 410 on which a single light emittingdie or chip 412 is surface-mounted to a level surface of the printedcircuit board 410. The printed circuit board 410 includes two printedcircuit traces 430, 431 disposed on the same surface as the lightemitting die 412. The two conductive traces 430, 431 can be formed bymetal evaporation or the like. Wire bonds 436, 437 connect top-sideelectrodes of the light emitting die or chip 412 with the conductivetraces 430, 431. The printed circuit board includes an insulative layer432 on which the two printed circuit traces 430, 431 are formed, and anoptional ground plate or metal core 438. A light transmissive cover 460covers the light emitting die or chip 412 and has an open end defining aperimeter 462 that is connected with the printed circuit board 410 todefine an interior volume 470 containing the light emitting die or chip412. The two printed circuit traces 430, 431 extend from inside thecover 460 to outside the cover 460 to provide electrical communicationinto the interior volume 470. A phosphor 472 optionally coats an insidesurface of the light transmissive cover 460, and an encapsulant 476substantially fills the interior volume 470. Hemispherical openings 480,482 formed at the perimeter 462 of the light transmissive cover 460allow for injection of the encapsulant material and correspondingdisplacement of air. That is, the openings 480, 482 of the lightingpackage 408 serve the same purpose as the printed circuit hoard openings80, 82 of the lighting package 8 (see FIG. 3).

With continuing reference to FIG. 11, a reflective coating 488 coats theinside surface of the light transmissive cover. The reflective coating488 is substantially reflective for light produced by the light emittingdie or chip 412 but is substantially transmissive for light produced bythe phosphor 472 responsive to illumination by the light emitting die orchip 412. In the lighting package 408, the phosphor 472 is disposed onthe reflective coating 488 and extends some distance into theencapsulant 476.

With reference to FIG. 12, another example embodiment lighting package508 is shown. A common printed circuit hoard 510 supports a plurality oflight transmissive dome-shaped covers 560 each covering one or morelight emitting dice 512. Printed circuitry of the common printed circuitboard 510 connects the light emitting dice 512 with edge terminals 446,447 that are adapted for connection with a DIN-type rail lightingfixture. In other contemplated embodiments, other types of terminals areemployed. For example, the electric terminals 46 shown in FIG. 1 can beused.

In some contemplated embodiments, the printed circuit board 510 is aflexible printed circuit board, so that the light source of FIG. 12 is aflexible sheet lighting source. In such flexible embodiments the lightemitting covers 560 provide mechanical protection for the light emittingdice 512. In some embodiments, the perimeter of each light transmissivedome-shaped cover 560 is secured to the flexible printed circuit boardin a manner so as to impart tensile strain to the portion of theflexible circuit board covered by the dome-shaped cover 560. In thisway, the portions of the flexible printed circuit board on which thelight emitting dice 512 are disposed are kept substantially rigid by thetensile strain as the flexible printed circuit board is flexed, thusreducing a likelihood that the flexing will break the connections orbonds of the light emitting dice 512 with the printed circuit board. Insome embodiments, the light transmissive dome-shaped covers 560 arearranged close together such that, together with light-dispersiveproperties of the covers 560, optional dispersive particles disposed inan encapsulant within the covers 560, light spreading provided by thedistribution of phosphor across the covers 560, or so forth, a spatiallyuniform planar lighting source 508 is formed that produces little or noperceptible pixilation of the illumination at typical illuminationsource-to-target distances.

One advantage of the lighting packaging techniques disclosed herein isflexibility in deployment of phosphor compositions. One or more phosphorlayers are readily disposed on the inner surface of the cover, forexample as described previously with respect to phosphorizationoperations 104, 310 of FIGS. 4 and 10, respectively. Application of alayer of phosphor to a glass or plastic cover surface can be done in aprecise and readily controllable manner. Each phosphor layer suitablyincludes a phosphor composition comprising one or more phosphorcompounds.

With reference to FIGS. 13 and 14, a lighting package 608 includes aprinted circuit board 610 supporting a light emitting die or chip 612,or optionally more than one light emitting die or chip, covered by alight transmissive cover 660. Thus, the lighting package 608 is similarto the lighting package 8 of FIGS. 1-3. However, the lighting package608 includes two phosphor layers L_(A), L_(B) of different phosphorcompositions disposed on an inner surface of the light-transmissivedome-shaped cover 660. The phosphor composition of phosphor layer L_(B)is different from the phosphor composition of layer L_(A) in that theyinclude at least one different phosphor compound. The lighting package608 optionally includes other features set forth herein with respect toother embodiments, such as an optional ultraviolet reflective coating688 diagrammatically shown in FIG. 14 disposed between the cover 660 andthe phosphor layers L_(A), L_(B). The ultraviolet reflective coating 688is useful for embodiments in which the light emitting die or chip 612emits ultraviolet light while the phosphor layers L_(A), L_(B) generatevisible light.

While two phosphor layers L_(A), L_(B) are illustrated, it will beappreciated that three or more phosphor layers can be provided so as toproduce light output which is a blend three or more phosphors. Thedome-shaped cover 660 provides a convenient platform for arranging one,two, or more phosphor layers each of which emits a spatially uniformdistribution of light subtending about 2π steradians or more.

It is contemplated to employ the layered approach of FIGS. 13 and 14 inconjunction with the tunable CRI concept discussed previously. Forexample, the first phosphor layer L_(A) may include a first constituentphosphor composition of blue, green, and yellow phosphor compounds A, B,and C, respectively, with a stoichiometry producing white orsubstantially white light at a first CRI value, while the secondphosphor layer L_(B) may include a second constituent phosphorcomposition of green, yellow, and red phosphor compounds B, C, and D,respectively, with a stoichiometry producing white or substantiallywhite light at a second, different CRI value. The layered combination ofthe first constituent phosphor composition of layer L, and the secondconstituent phosphor composition of layer L_(B) produces a CRI valuethat is different from, and possibly larger than, the first or secondCRI value.

CRI tuning using a single layer containing two or more constituentphosphor compositions of about the same color point has been describedwith example reference to FIG. 3. CRI tuning using a layered structurein which each layer contains one of the constituent phosphorcompositions of about the same color point has been described withexample reference to FIGS. 13 and 14. The two or more constituentphosphor compositions whose light is blended to produce a tailored CRIand/or luminosity can be combined in other physical arrangements, suchas being disposed as distinct patterns in a single layer.

With continuing reference to FIGS. 13 and 14, in some cases one of thephosphor compositions may become saturated at high levels of irradiationintensity by the light emitting die or chip 612. The layered arrangementof FIGS. 13 and 14 can also be useful in addressing such saturationissues. The more easily saturated phosphor composition is suitablyarranged as the phosphor layer L_(A) that is furthest from the lightemitting die or chip 612, since partial absorption of light by theintervening phosphor composition of phosphor layer L_(B) can be expectedto reduce the excitation light flux of the phosphor composition in layerL_(A), thus facilitating more efficient light conversion.

It is to be appreciated that the phosphors can be disposed in otherspatially separated arrangements besides layers. For example, in someembodiments, the first phosphor composition may be arranged physicallyas a layer disposed on an inside or outside surface of thelight-transmissive cover, while the second phosphor composition may bedispersed in an encapsulant filling the interior volume.

With reference to FIG. 15, a light-transmissive cover having other thana dome-shaped geometry can be employed. FIG. 15 shows a lighting package708 that includes a printed circuit board 710 supporting a lightemitting die or chip 712, or optionally more than one light emitting dieor chip, covered by a light transmissive cover 760. Thus, the lightingpackage 708 is similar to the lighting package 608 of FIGS. 13 and 14,except that the light-transmissive cover 760 has a different geometrythan the dome-shaped cover 660 of FIGS. 13 and 14. Thelight-transmissive cover 760 includes a reflective side portion orportions 760 _(R) that channel light (indicated diagrammatically in FIG.15 by two drawn rays) toward a light-transmissive top portion 760 _(T).Two phosphor layers L_(X), L_(Y) of different phosphor compositions(that is, having at least one different phosphor compound) are disposedon the light-transmissive top portion 760 _(T). Optionally, the twophosphor layers L_(X), L_(Y) may also extend along the inside of thereflective side portion 760 _(R) of the light-transmissive cover 760. Insome contemplated embodiments, the phosphor layers are disposed only onthe inside reflective side portion 760 _(R) of the light-transmissivecover 760, while the light-transmissive top portion 760 _(T) is leftuncoated by phosphor. In those of such embodiments that employ anultraviolet-emitting die or chip 712, the light-transmissive top portion760 _(T) is preferably absorbing or reflective for ultraviolet light toprevent direct ultraviolet light from being emitted from the lightingpackage 708.

With reference to FIG. 16, depending upon how the phosphor layer orlayers are disposed on the light-transmissive cover, a logo, picture,symbol, pattern, or other depiction can be generated. FIG. 16 shows aperspective view of another lighting component or package similar tothat of FIGS. 1-3, but having two different phosphor compositionsdisposed on different regions 800, 802 screen-printed on thelight-transmissive dome-shaped cover 60. The screen-printed phosphorregion 800 spells out “Acme Corp.” along with a corresponding logo,while the screen-printed phosphor region 802 covers the area of thelight-transmissive dome-shaped cover 60 not covered by the phosphorregions 800. If for example, the phosphor composition of the region 800emits red light while the phosphor composition of the region 802 emitswhite light, then when the one or more light emitting dice or chipswithin the cover 60 are energized, the name “Acme Corp.” andcorresponding logo appears in as a red light-emissive text and symbol ona white light emissive background. Advantageously, when using twodifferent phosphor compounds in respective regions to define the logo,picture, symbol, pattern, or other depiction, both the foreground (e.g.,text or logo artwork) and the background are light-emissive.

Some additional embodiments are disclosed as follows.

Although the discussion below with respect to embodiments of the presentinvention is directed to LEDs for convenience, it should be understoodthat the invention relates to the use of any light emittingsemiconductor. With reference to FIG. 17, a conventional LED assembly isshown generally at 1010.

The LED assembly includes an LED chip 1012 mounted on a bottom surface1014 of the LED assembly. The LED chip 1012 emits radiation (typicallyUV or blue light in a white light LED). A lens 1018 made from atransparent material surrounds the chip 1012 and bottom surface 1014.Two lead wires 1020 connect the chip 1012 to a source of power. Fillingthe space 1022 between the lens and the chip 1012 is typically an epoxyor other transparent material (not shown). Intimately dispersed withinthe epoxy are phosphor particles (not shown) that absorb at least aportion of the emitted by the chip 1012 and converting it to a differentwavelength.

With reference to FIG. 18, a cross-sectional view of an embodiment isshown. In this embodiment, an LED package is provided generally at 1110and includes an LED chip 1112 mounted on a submount 1114, which in turnis mounted on a reflector 1116. As used herein, “reflector” is meant toinclude not only any surface on the bottom of the LED package, but alsoany other structures meant to support the LED chip, e.g. a heat sink,etc. A lens 1118 made from a transparent material surrounds the chip1112 and submount 1114 and reflector 1116. Optionally filling space 1122between the lens and the chip 1112 is typically an epoxy or othertransparent material. A phosphor layer 1124 comprising phosphorparticles is applied on an inside or outside surface of the lens 1118.The coating is preferably coated on an inside surface of the lens toprevent the phosphor coating from being displaced by handling, etc. Thethickness of the phosphor coating should be sufficient to convert atleast a portion of the radiation emitted by the LED chip to a differentwavelength. This thickness may typically be between 6-200 μm, with apreferred thickness being between 20-30 micron μm.

The LED chip 1112 can be any conventional UV or blue light LED. SuchLEDs are known and typically consist of InGaN or AlGaN layersepitaxially grown on a sapphire, alumina or single crystal SiCsubstrate. A preferred LED chip may have a primary emission in the rangeof 200-480 nm. Likewise, the phosphor layer 1124 may include one or moresuitable fluorescent phosphors capable of absorbing the UV or blueradiation and in turn of producing, either alone or in combination withthe radiation emitted by the LED chip, a visible white or near-whitelight for illumination. Suitable phosphors for use in the presentinvention include, but are not limited to, Y₃AI₅O₂:Ce (YAG:Ce),Tb₃AI_(4.9)O₁₂:Ce (TAG:Ce), and Sr₄AI₁₄O₂₅:Eu (SAE). Other white lightproducing phosphors are also suitable. The size of the phosphorparticles is not critical, and may be, by way of example, about 3-30 μmin diameter.

The lens 1118 may be made from any material that is substantiallytransparent to the radiation emitted by the phosphor and the LED chip.Thus, depending on the wavelength of the emitted radiation, the lens maycomprise various materials including, but not limited to, glass, epoxy,plastic, thermoset or thermoplastic resins, or any other type of LEDencapsulating material known in the art.

The providing of the phosphor coating 1124 on an inside surface of thelens 1118 rather than dispersed in the epoxy or other fill materialprovides a more uniform and efficient conversion of the LED emission.One advantage is that a uniform coating of controlled thickness may beapplied. One benefit of this is that coating thickness can be accuratelycontrolled for optimum conversion efficiency and UV bleed through (if aUV emitting chip is used) control using a minimum amount of phosphor.This helps to achieve uniform light emission without incidence of colorrings resulting from non-uniform dispersion of the phosphor in prior artdevices. Another benefit is that the phosphor is remote from the heatgenerated by the LED, further increasing the conversion efficiency. Ofcourse, the phosphor layer may be positioned inside the lens material orhave a coating of another material positioned over it, and such anarrangement is contemplated herein.

Although not intended to be limiting, the phosphor coating may beapplied by, for example, spray coating, roller coating, meniscus or dipcoating, stamping, screening, dispensing, rolling, brushing or sprayingor any other method that can provide a coating of even thickness. Apreferred method for applying the phosphor is by spray coating.

In an exemplary technique for coating the lens and reflector parts ofthe LED housing, the phosphor powder is first stirred into a slurry,along with a binder and a solvent. Suitable binders include, but are notlimited to, silicone, epoxies, thermoplastics, acrylics, polyimides, andmixtures thereof. Suitable solvents include, but are not limited to, lowboiling point solvents such as toluene, methyl ethyl ketone (MEK),methylene chloride, and acetone. The amount of each component in theslurry is not critical, but should be chosen so as to produce a slurrythat is easily applied to the lens while also containing a sufficientconcentration of phosphor particles for efficient conversion of the LEDradiation. An exemplary slurry can be made using about 2 parts by weightof a 6 μm phosphor, 1.2 parts silicone, and 1 part MEK. A suitablesilicone is GE XE5844.

The slurry is subsequently applied to the surface of the lens. Thecoated lens may then be baked, heated or otherwise treated to remove thesolvent and cure the binder. As used herein, the term “cure” is meant toencompass not only actual curing or crosslinking of the binder, but alsomore generally to indicate any chemical and/or physical change in thebinder to a state in which the phosphor particles become relativelystationary in the hinder, typically due to a solidifying or hardening ofthe binder.

As noted above, the slurry can be applied to the lens via any suitablemethod. In a preferred method, the slurry is applied by spray coating.In this method, the slurry is used to fill the reservoir of a suitableair brush. The slurry is then sprayed using a pressurized spray gun ontothe lens, which is preheated and kept on a hot plate at an elevatedtemperature preferably above the boiling temperature of the solvent, forexample at about 110° C. The part is sprayed by making successivepasses, which may be done at about ½ second per pass. The slurry drieson contact and a uniform coating is achieved. A coating approximately 4layers thick (about 20-30 μm using 6 μm size phosphor particles) isachieved on the lens with 35-40 passes. The lens is then baked to curethe binder. It is planned that this approach to coating LED's would beused for any LED's for general illumination. If desired, a secondcoating of a transparent material may be added over the phosphor layerto protect the phosphor or to provide an overcoating to help lightextraction.

A significant improvement in light output has been achieved using blueLED's with the YAG phosphor over the conventional coating method whereinthe phosphor is embedded in the slurry and uniformly applied around thechip. Clearly there are many other ways to remotely the lens surroundingan LED chip. These would be considered within the scope of thisinvention.

In one preferred embodiment, the lens preferably has a radius that is atleast about 2-3 times the length (“L”) of one side of the chip. Thisarrangement increases the likelihood that radiation generated orreflected off a coating applied to such a lens is more likely to strikeother parts of the coating, where it will be retransmitted, rather thanthe chip or other non-coated area, where it will be absorbed and lost.

In a second embodiment, illustrated in FIG. 19, an LED package is againprovided at 1210 and includes an LED chip 1212 mounted on a submount1214, which in turn is mounted on a reflector 1216. A lens 1218surrounds the chip 1212 and submount 1214 and reflector 1216. Optionallyfilling space 1222 between the lens and the chip 1212 is typically anepoxy or other transparent material. To further improve efficiency, aphosphor coating 1224 comprising phosphor particles is applied on aninside surface of the lens 1218 and on the top surface of the reflector1216. The top surface of the reflector, which may be thought of as thebottom of the package, is preferably first coated with a reflectivelayer 1240, such as a high dielectric powder, such as, alumina, titanic,etc. A preferred reflective material is Al₂O₃. The phosphor layer 1224is then placed over the reflective layer 1240 on top of the reflector.The use of the reflective layer 1240 serves to reflect any radiation1242 that penetrates the phosphor layer 1224 on this surface.Alternately, instead of coating the transparent lens 1218 with aseparate phosphor layer 1224, the phosphor may instead be intimatelydispersed within the material comprising the transparent hemisphere.

The phosphor layer 1224 over the reflective layer 1240 on the reflector1216 is preferably relatively thick, i.e. greater than 5 layers ofpowder, while the phosphor layer on the curved top of the hemisphere maybe adjusted to achieve a desired color and to absorb all radiationincident on it. In general the phosphor layer on the top of thehemisphere will range between 1-4 layers thick in the case of blueemitting chips in order that some of the blue radiation be emitted. Inthe case of UV chips the layer of phosphor coating on the hemisphereshould be 4-8 layers thick in order to absorb at least most of the UVradiation emitted by the chip.

As shown in FIG. 19, radiation from the chip 1242 is prevented fromleaving the structure without first striking the phosphor coated surfaceof the hemisphere. Further, the total phosphor coated surface area ismuch greater than the surface area of the emitting chip, preferably atleast 10 times the exposed surface area of the absorbing parts of theLED chip. As used herein, the exposed surface area of the absorbingparts of the LED include the exposed surface are of the LED chip as wellas any exposed surface of the submount not covered with a reflectivelayer and/or a phosphor layer.

In such an arrangement, although there may be a significant amount ofblue or UV radiation scattered back into the hemisphere, nearly all thisradiation, which is diffusely scattered, strikes other parts of thephosphor coating rather than the chip or submount. Most of the visiblelight generated by the phosphor coating also is directed back into thehemisphere. Also there is no metallic reflector and no exposed leadstructure. The important feature of this geometry is that everythingexcept the LED chip 1212 is phosphor covered and the phosphor surfacearea of the hemisphere is much larger, preferably greater than 10 times,the surface area of any absorbing parts of the LED. Therefore, nearlyall radiation going back into the hemisphere will strike otherphosphor-coated areas and be either reflected or absorbed andretransmitted by the phosphor. The embodiments disclosed herein arecalculated to have an efficiency greater than 70%, and in most casesapproaching 100%.

In Table 1 the efficiency of this design is compared with severalstandard LED package geometries. These comparisons were made using acomputer simulation. The computer simulation is a flux model describedbelow. It considers all the radiation fluxes and assumes that all arediffuse so that the amount of radiation incident on any given surface isproportional to its area. As shown in Table 1 the geometry describedabove provides a package efficiency of essentially 100%.

TABLE 1 Comparison of Calculated Package Efficiencies of Two StandardConfigurations of Phosphor Coated LED's with 3 Embodiments Disclosed inthe Present Invention Package Milliwatts/ Efficiency lumen SiC Al₂O₃ SiCAl₂O₃ LED Description substrate substrate substrate substrate 1.6 mm²chip + 27 mm² 58% 70% 6.7 5.6 reflector + phosphor on chip 1.6 mm²chip + 69% 80% 5.7 4.9 phosphor on chip 1.6 mm² chip + 27 mm² 82% 88%4.7 4.4 reflector + phosphor on lens (FIG. 5) 1.6 mm² chip + 3 mm 98%99% 4 3.9 radius hemisphere (FIG. 3) 1.6 mm² chip + 3 mm 99% 100% 3.93.9 radius sphere (FIG. 4)

FIG. 20 shows an embodiment operating under the same principle. Here anLED chip 1312 is mounted on a pedestal 1314 which also serves as theheat sink. However, the chip 1312 is placed at the center of a moldedsphere 1318. A phosphor layer (not shown) is then coated on the insidesurface 1320 of the sphere 1318 or, alternately, intimately dispersedwithin the sphere. In this design the LED will radiate uniformly in alldirections. Again, it is clear that both blue/UV radiation and visibleradiation generated by the phosphor coating and scattered back into thesphere will be more likely to strike other phosphor coated surfaces inpreference to striking either the chip 1312 or the pedestal 1314. Theselight absorbing structures are small targets for the diffuse radiation.As seen in Table 1, the package efficiency is close to 100% for thisarrangement. The lower package efficiency for LED structure on SiCsubstrates are due to greater absorption of the LED radiation by the SiCsubstrate as compared to the Al₂O₃ substrate.

From the previous embodiments, It is apparent that the specific shape ofthe phosphor coating is not important as long as it surrounds ascompletely as possible the LED chip and is a distance sufficient fromthis chip (e.g. a distance such that the phosphor coated surface has asurface area greater than about 10 times the exposed surface area of thechip) such that radiation scattered from the coating is unlikely tostrike the chip or chip structures. The invention is not limited to theembodiments described herein but intended to embrace all such coatingshapes, and preferably wherein the phosphor covered surfaces hasapproximately 10 times the exposed area of the absorbing parts of theLED or greater. Thus, the lens on which the phosphor is coated is notlimited to hemispherical or spherical, but can include any geometricshape, preferably with the phosphor coated surface area being about atleast 10 times the exposed area of the absorbing parts of the LED.

The invention is also intended to cover geometries which are not soideal and perhaps do not give the full advantage of 100% packageefficiency but nevertheless do utilize the principle of a remotephosphor coating designed so that the coated surface is at least 10times the emitting area of the chip. For example FIG. 21 shows aschematic of a conventional surface mount LED. In this arrangement, theLED chip 1412 and submount 1414 are mounted in a reflector cup 1416.Unlike the conventional design, which has the phosphor embedded more orless randomly in an optical medium between reflector and the lens, thephosphor coating is applied as a layer on a transparent lens 1418. Thephosphor coating is remote from the chip 1412 and on a surface withabout >10 times the exposed area of the absorbing parts of the LED.Obviously, the surface of the lens 1418 on which the phosphor coating isapplied can have a surface area less than 10 times the surface area ofthe chip. However, the package efficiency of the assembly will bereduced accordingly, since more of the radiation will strike and beabsorbed by the chip. A second lens 1430 can be mounted over thephosphor coated lens for protection.

Most of the UV or blue radiation and visible radiation which isscattered hack from the phosphor coating strikes either the reflectorcup 1416 or other phosphor surface. Only a relatively small amountstrikes the light absorbing chip and submount. In this design it isimportant that the reflector cup 1416 be made of a very highlyreflective material, for example a vapor deposited and protected silvercoating with greater than 95% reflectivity or an inorganic powder ofhigh purity, such as finely divided alumina or titania. In addition thereflector cup 1416 may or may not be coated with the phosphor. Table 1shows the simulated performance of a specific LED with an area of 1.6mm² on a submount in a silver reflector cup utilizing a phosphor coatedlens of area of 27 mm².

As shown in FIGS. 22 and 23, the present invention also discloses theconcept of a remote phosphor coating as applied to systems containingmultiple LED chips. Multiple blue or UV emitting LED's can be mounted ona single reflective electrical interconnect board or other structure. Aphosphor coated surface then is used to surround not a single LED butthe entire set of LED's. The phosphor coated surface may be used aloneor in combination with other highly reflecting surfaces to surround theset of LED's. Two examples of such structures are shown in FIGS. 22 and23. One is a power module 1500 which might be used as a downlight. Theother is a panel lamp 1600 with many LED's 1602 mounted behind aphosphor coated panel 1604. It is clear that many such arrangementscould be made provided that the phosphor surface area is the preferred10 times the exposed area of the absorbing parts of the LED.

As detailed above, any of the embodiments may include an epoxy or othertransparent filler between the LED chip and the phosphor coated lens.More efficient extraction of light can be realized when the refractiveindex of the encapsulant or transparent filler is closely matching thegeometric mean of the refractive indexes of the die and the lens,preferably within about 20% of this value, and even more preferablywithin about 10%. This reduces the amount of internal reflections in thelamp. Thus, in the case of a GaN LED chip having a refractive index ofabout 2.7 with a lens having a refractive index of about 1.5, the fillerwill preferably have a refractive index of from about 2.1. In the caseof an LED chip having two or more materials having different refractiveindices, such as a GaN semiconductor on a sapphire submount having arefractive index of about 1.7, the refractive index of the encapsulantwill preferably match the geometric mean of the lens and the higher ofthe two. Better light extraction can thus be achieved with encapsulantshaving a higher index of refraction than epoxy, such as spin-on glass(SOG) or other high refractive index materials.

Any of the above embodiments can also be equipped with one or more baudpass filters to further improve the efficiency of the resulting LEDpackage. Thus, in one embodiment, as shown in FIG. 25, a lens 1718 for ablue LED source is shown containing a first band pass filter 1750. Theband pass filter is positioned between the phosphor layer 1724 and theLED (not shown). The band pass filter is selected such that the incidentlight 1752 from the blue LED source is allowed to pass while the light1754 emitted from the phosphor layer 1724 is reflected outward.

In the embodiment shown in FIG. 26, two band pass filters are providedin a UV LED source package. In this embodiment, a first hand pass filter1850 is positioned between the phosphor layer 1824 and the LED source(not shown) adjacent a lens 1818. The first band pass filter acts totransmit the UV light 1852 from the LED while reflecting the light 1854emitted from the phosphor layer 1824. A second band pass filter 1856reflects the UV light 1852 from the LED while allowing the light 1854emitted from the phosphor layer 1824 to pass. This arrangement preventsthe transmission of potentially harmful UV radiation from the packagewhile ensuring transmission of visible light.

As seen in FIG. 27, an array of micro or macro lenses 1960 may be formedon the outer surface of the lens 1918 in any of the above embodiments tocontrol the emission angle, direction or intensity of the emittedradiation 1952 and 1954.

The calculation results shown in Table 1 are based on a linear fluxmodel illustrated in the FIG. 24. The figure shows nine fluxes incidenton four surfaces of the LED package. These fluxes are described by thenine linear equations below, with each equation describing the flux withthe corresponding number. The equations are:

Flux  F 1:  L₃^(out) = L₃⁺t₃^(VIS)${{Flux}\mspace{14mu} F\; 2\text{:}\mspace{20mu} L_{3}^{-}} = {{L_{3}^{+}r_{3}^{VIS}} + {I_{3}^{+}a_{3}^{UV}{Q\left( {{\overset{\_}{\lambda}}_{I}/{\overset{\_}{\lambda}}_{L}} \right)}\left( \frac{1}{2} \right)}}$${{Flux}\mspace{14mu} F\; 3\text{:}\mspace{20mu} L_{3}^{+}} = {{L_{2}^{-}p_{23}} + {L_{1}^{-}p_{13}} + {L_{0}^{-}p_{03}} + {I_{3}^{+}a_{3}^{UV}{Q\left( {{\overset{\_}{\lambda}}_{I}/{\overset{\_}{\lambda}}_{L}} \right)}\frac{1}{2}}}$${{Flux}\mspace{14mu} F\; 4\text{:}\mspace{20mu} L_{2}^{+}} = {{L_{3}^{-}p_{32}} + {L_{1}^{-}p_{12}} + {L_{0}^{-}p_{02}} + {I_{2}^{+}a_{2}^{UV}{Q\left( {{\overset{\_}{\lambda}}_{I}/{\overset{\_}{\lambda}}_{L}} \right)}\frac{1}{2}}}$Flux  F 5:  L₂⁻ = L₂⁺r₂^(VIS) Flux  F 6:  L₁⁺ = L₃⁻p₃₁ + L₂⁻p₂₁ + L₀⁻p₀₁Flux  F 7:  L₁⁻ = L₁⁺r₁^(VIS) Flux  F 8:  L₀⁺ = L₃⁻p₃₀ + L₂⁻p₂₀ + L₁⁻p₁₀Flux  F 9:  L₀⁻ = L₀⁺r₀^(VIS)These surfaces are:

3=the upper phosphor coated surface,

2=the lower phosphor coated surface,

1=the reflector and submount, and

0=the blue or UV emitting chip.

There are nine other equations describing the blue or UV fluxes. Theequations describing the blue or UV fluxes are not shown. They arecoupled to the visible light equations through the quantum efficiency Qand the Stoke's s shift (λi/λI). The eighteen linear equations result ineighteen unknowns, i.e. the relative powers of radiation striking eachsurface, and are solved simultaneously.

The p values are the probabilities that radiation from one surface willstrike another. In the calculations shown in Table 1 these were taken tobe the ratios of surface areas. Q is the quantum efficiency of thephosphor. λ is the average wavelength of the blue or UV chip radiationor the average wavelength of the visible emission of the phosphor.

The other parameters needed are the reflectivities and absorptivities ofthe different material surfaces. These were obtained either fromHandbook values or were measured directly using known methods. There areno values for the reflectivities of the chips and so these werecalculated by assuming that each chip consisted of the semiconductorlayers and substrate. All radiation incident on the chip was assumed tobe normal and incident on the substrate in a flip-chip design anddiffraction effects were ignored. Up to second order the expression forthe reflectivity of the chip is then:R=R _(sub)+(1−R _(sub))²exp(−2a _(sub) t _(sub))R _(act)+(1−R_(Sub))²exp(−2a _(sub) t _(sub))(1−R _(act))²exp(−2a _(act) t _(act))R_(mst) . . .where:

-   R_(sub)=reflectivity of substrate R_(act)=reflectivity of active    layers-   a_(sub)=absorption cost of sub a_(act)=absorption coefficient of    active layers-   t_(sub)=thickness of substrate t_(act)=thickness of active layers    Known or estimated values were used for the indices of refraction,    the absorption coefficients and thicknesses. Thus,    R=((n1−n2)² +k ²)/(n1+n2)² +k ²), where k=λa/2π.

The invention has been described with reference to the preferredembodiments. Obviously, modifications and alterations will occur toothers upon reading and understanding the preceding detaileddescription. It is intended that the invention be construed as includingall such modifications and alterations insofar as they come within thescope of the appended claims or the equivalents thereof.

1. A lighting apparatus comprising: a support surface; a light sourcecomprising at least one light emitting diode (LED) chip, the lightsource being disposed on the support surface; a light transmissive bodyincluding a phosphor, said body being disposed over and spaced apartfrom the light source, the phosphor configured to perform wavelengthconversion of light emitted by the light source; and reflecting surfacesextending between the support surface and the light transmissive body;wherein the support surface, the light transmissive body, and thereflecting surfaces are arranged and dimensioned respective to the lightsource such that most light scattered back from the phosphor strikeseither the reflecting surfaces or the light transmissive body.
 2. Thelighting apparatus as set forth in claim 1, wherein the lighttransmissive body is arcuate having a perimeter larger than a perimeterof the support surface, and the reflecting surfaces extend between thesmaller perimeter of the support surface and the larger perimeter of thearcuate light transmissive body.
 3. The lighting apparatus as set forthin claim 1, wherein the reflecting surfaces comprise at leastsubstantially transverse reflecting surfaces that are at leastsubstantially transverse to the support surface.
 4. The lightingapparatus as set forth in claim 3, wherein the transverse reflectingsurfaces extend at a nonperpendicular angle between a smaller perimeterof the support surface and a larger perimeter of the light transmissivebody.
 5. The lighting apparatus as set forth in claim 1, wherein thereflecting surfaces include a reflector cup containing the light source.6. The lighting apparatus as set forth in claim 5, wherein thereflecting surfaces further include one or more reflecting surfacesother than the reflecting cup that extend between the reflector cup andthe light transmissive body.
 7. The lighting apparatus as set forth inclaim 1, wherein the support surface is planar and the lighttransmissive body is spaced apart from the plane of the support surface,and the reflecting surfaces include reflective sidewalls extending fromthe planar support surface to the light transmissive body.
 8. Thelighting apparatus as set forth in claim 7, wherein the reflectivesidewalls include slanted reflective sidewalls.
 9. The lightingapparatus as set forth in claim 7, wherein the light transmissive bodycomprises a planar phosphor inclusive surface spaced apart from planarsupport surface.
 10. The lighting apparatus as set forth in claim 1,wherein the light source comprises an elongated light source comprisinga plurality of LED chips distributed on and over a length of anelongated support surface, and the light transmissive body haselongation commensurate with the elongation of the elongated supportsurface.
 11. The lighting apparatus as set forth in claim 10, whereinthe reflecting surfaces include reflective sidewalls extending from theelongated support surface to the elongated light transmissive body. 12.The lighting apparatus as set forth in claim 1, wherein the lightingapparatus is oriented as a downlight.
 13. The lighting apparatus as setforth in claim 1, wherein the support surface comprises a reflectivesupport surface.
 14. A lighting apparatus comprising: at least one lightemitting diode (LED) chip; and a light mixing chamber includingreflecting surfaces defining a light output aperture of the light mixingchamber and a light transmissive body including a phosphor, said lighttransmissive body being disposed over the light output aperture of thelight mixing chamber, the phosphor configured to perform wavelengthconversion of light emitted by the at least one LED chip; wherein the atleast one LED chip is disposed in the light mixing chamber and is spacedapart from the light transmissive body such that most light scattered inthe light mixing chamber strikes either the reflecting surfaces or thelight transmissive body.
 15. The lighting apparatus as set forth inclaim 14, wherein the reflecting surfaces have reflectivity of greaterthan 95%.
 16. The lighting apparatus as set forth in claim 14, whereinthe at least one LED chip comprises a set of LED chips and the lighttransmissive body including a phosphor comprises a phosphor panel behindwhich the set of LED chips is mounted.
 17. The lighting apparatus as setforth in claim 16, wherein the reflecting surfaces in combination withthe phosphor panel surround the set of LEDs.
 18. The lighting apparatusas set forth in claim 17, wherein the reflecting surfaces do notcomprise phosphor.
 19. The lighting package as set forth in claim 14,wherein the reflecting surfaces comprise a reflector cup.
 20. A lightingapparatus comprising: a light source comprising a set of (LED) chipsdisposed on an electrical interconnect board; a phosphor surface spacedapart from the light source, the phosphor surface comprising phosphorconfigured to perform wavelength conversion of light emitted by thelight source; and reflecting surfaces not comprising phosphor combiningwith the phosphor surface to surround the set of LEDs.
 21. The lightingapparatus as set forth in claim 20, wherein the reflecting surfaces andthe phosphor surface are arranged and dimensioned respective to thelight source such that most light scattered back from the phosphorsurface strikes either the reflecting surfaces or the phosphor surface.22. The lighting apparatus as set forth in claim 20, wherein theelectrical interconnect board is a reflecting electrical interconnectboard and the reflecting surfaces include the reflecting electricalinterconnect board.
 23. The lighting apparatus as set forth in claim 20,wherein the set of LEDs comprises multiple blue or UV emitting LEDs. 24.The lighting apparatus as set forth in claim 20, wherein the lightingapparatus comprises a downwardly oriented downlight.
 25. The lightingapparatus as set forth in claim 20, wherein the lighting apparatuscomprises a panel lamp in which the phosphor surface comprises aphosphor panel and the set of LEDs is mounted behind the phosphor panel.26. A lighting apparatus comprising: a support surface; a light sourcecomprising at least one light emitting diode (LED) chip, the lightsource being disposed on the support surface; an arcuate phosphorsurface comprising phosphor disposed over and spaced apart from thelight source, said phosphor surface having a perimeter larger than aperimeter of the support surface, the phosphor configured to performwavelength conversion of light emitted by the light source; andreflecting surfaces extending between the smaller perimeter of thesupport surface and larger perimeter of the phosphor surface; whereinthe support surface, the phosphor surface, and the reflecting surfacesare arranged and dimensioned respective to the light source such thatmost light scattered back from the phosphor surface strikes either thereflecting surfaces or the phosphor surface.